How to Safely Connect a Generator to Your House (2024)

TL;DR: Never plug a portable generator into a wall outlet — that's called backfeeding and it can electrocute utility workers restoring power on the line. The only safe, code-compliant way to connect a generator to your house is a transfer switch (manual or automatic), which costs roughly $400 to $900 for a manual unit installed by an electrician, or $2,500 to $5,000 for a whole-house automatic system. Skipping the switch also risks frying your generator and voiding your homeowner's insurance if it causes a fire.

_Last reviewed: July 2026 · 7 min read_

The power's out, the freezer's warming up, and you've got a generator in the garage but no idea how to get it talking to your house without doing something dangerous. Most people's first instinct — running an extension cord to an outlet, or worse, plugging the generator into a dryer outlet — is exactly the move that gets people killed or fined. Here's the safe way to do it.

Okoniq Property Hub keeps a record of your transfer switch install date, generator maintenance schedule, and permit paperwork so nothing gets lost between outages.

Why is backfeeding a generator so dangerous?

Backfeeding means plugging a generator into a regular wall outlet or a 240-volt dryer outlet using a "suicide cord" — a cable with male plugs on both ends. It sends power backward through your house wiring, out through the meter, and onto the utility line outside.

That line is normally dead during an outage, which is why crews work on it without full protection. A backfed generator can energize it at your generator's voltage, and step-up through neighborhood transformers can push it to over 7,000 volts on the pole side. Linemen have died this way. It's also illegal in most jurisdictions and will void your homeowner's insurance if a fire or injury results. Beyond the danger to others, backfeeding with no isolation from utility power can also destroy your generator the instant utility power returns, since the two sources fight each other.

If your panel is older or already stretched thin, it's worth checking whether you have enough electrical capacity before adding any generator load at all.

What's the right way to connect a generator — a transfer switch?

Yes, a transfer switch is the only method that's both safe and legal in nearly every state and municipality. It physically isolates your house circuits from the utility line before generator power flows in, so backfeeding is impossible.

There are two main types. A manual transfer switch, installed near your main panel by a licensed electrician, lets you flip a set of breakers to choose which circuits (lights, fridge, furnace fan, a few outlets) run off the generator. Installed cost typically runs $400 to $900, plus $200 to $500 for a compatible inlet box mounted outside your house so you never run a cord through a window or door.

An automatic transfer switch (ATS) pairs with a standby generator that's wired permanently to your house and starts itself within 10 to 20 seconds of an outage. These systems run $2,500 to $5,000 for equipment plus $3,000 to $7,500 or more for the whole-house generator itself, installed. A cheaper alternative some homeowners use is an interlock kit, a metal plate that physically prevents the main breaker and generator breaker from being on at the same time, costing $75 to $200 for parts. Interlocks are legal in many areas but not all, so check with a local electrician or your building department first.

Do I need a permit or inspection to install one?

In most US municipalities, yes. Transfer switch installs typically require an electrical permit and an inspection, because the work involves tying into your main panel and, for standby systems, running a dedicated circuit and sometimes a gas or propane line.

Permit costs usually range from $50 to $300 depending on your city, and skipping this step can cause problems later: a home inspector or insurance adjuster who finds an unpermitted generator hookup during a claim can deny coverage related to the electrical system. If your house still has older wiring, this is also a good moment to have an electrician check for knob-and-tube wiring, since that type of wiring isn't rated for the loads a generator hookup can introduce.

| Manual Transfer Switch | Automatic Standby System | |---|---| | $400-$900 installed | $5,500-$12,500+ installed | | You start generator manually | Starts itself in 10-20 seconds | | Powers select circuits only | Can power whole house | | Portable generator, store when not in use | Permanent unit, runs on natural gas or propane |

What size and setup does the generator itself need?

Match the generator's running wattage to what you actually plan to power, not your whole house. Add up the running watts of your fridge (roughly 150-800W), furnace blower (300-800W), a few lights and a sump pump, and most households land comfortably in the 3,500 to 7,500 watt range for a portable unit, with some cushion for the higher startup surge motors need when they kick on.

Run portable generators outdoors, at least 20 feet from windows and doors, never in a garage even with the door open. Carbon monoxide from a generator can build to lethal levels indoors in minutes, and CO detectors save lives here — put one on every level of the house if you don't already have them. Also check that any outdoor outlets or extension cords you use for smaller appliances have proper grounding; if your house still has 2-prong outlets instead of grounded 3-prong ones, that's worth fixing before storm season regardless of a generator.

FAQ

Can I just run an extension cord from my generator into the house?

You can power individual appliances this way with heavy-duty outdoor-rated cords rated for the generator's amperage, but you cannot connect the generator to your house wiring or panel this way. That's backfeeding and it's both dangerous and illegal.

How much does a whole generator hookup cost start to finish?

For a portable generator with a manual transfer switch and inlet box, budget $600 to $1,400 total including the electrician's labor and permit. A permanent standby system with automatic transfer switch runs $6,000 to $12,000 or more depending on generator size and home wattage needs.

Is an interlock kit as good as a transfer switch?

An interlock kit accomplishes the same safety goal, preventing simultaneous utility and generator power, for a fraction of the cost, often $75 to $200 in parts plus an hour or two of electrician labor. Check with your local building department first since some jurisdictions don't permit interlocks for code compliance reasons.

How often should I test my transfer switch and generator?

Run the generator under load for 15-20 minutes every 30 days, and do a full transfer switch test twice a year, ideally before summer storm season and before winter. Stale gasoline and dead batteries are the top two reasons generators fail to start when actually needed.

What size wire and inlet do I need for the connection?

That depends on your generator's amperage output, typically a 30-amp locking inlet for generators up to about 7,500 watts, or a 50-amp inlet for larger units. An electrician will size the wire gauge to match, and this isn't a spot to guess since undersized wire can overheat.

This is educational information, not electrical or safety advice. Call a licensed electrician to size and install your transfer switch, and check with your local building department on permit requirements before starting any work.